Modern hearing assistance devices typically include digital electronics to enhance the wearer's experience. Whether due to a conduction deficit or sensorineural damage, hearing loss in most patients occurs non-uniformly over the audio frequency range, most commonly at high frequencies. Hearing aids may be designed to compensate for such hearing deficits by amplifying received sound in a frequency-specific manner, thus acting as a kind of acoustic equalizer that compensates for the abnormal frequency response of the impaired ear. Adjusting a hearing aid's frequency-specific amplification characteristics to achieve a desired level of compensation for an individual patient is referred to as fitting the hearing aid. One common way of fitting a hearing aid is to measure hearing loss, apply a fitting algorithm, and fine-tune the hearing aid parameters.
Hearing assistance devices also use a dynamic range adjustment, called dynamic range compression, which controls the level of sound sent to the ear of the patient to normalize the loudness of sound in specific frequency regions. The gain that is provided at a given frequency is controlled by the level of sound in that frequency region (the amount of frequency specificity is determined by the filters in the multiband compression design). When properly used, compression adjusts the level of a sound at a given frequency such that its loudness is similar to that for a normal hearing person without a hearing aid. There are other fitting philosophies, but they all prescribe a certain gain for a certain input level at each frequency. It is well known that the application of the prescribed gain for a given input level is affected by time constants of the compressor. What is less well understood is that the prescription can break down when there are two or more simultaneous sounds in the same frequency region. The two sounds may be at two different levels, and therefore each should receive different gain for each to be perceived at their own necessary loudness. Because only one gain value can be prescribed by the hearing aid, however, at most one sound can receive the appropriate gain, providing the second sound with the less than desired sound level and resulting loudness.
Current hearing aid designs employ digital signal processors rich in features. The operation and maintenance of wireless hearing aids may be improved or simplified by improving the wireless communication components within the hearing aid. Some wireless hearing aids have sought to improve wireless performance by using various wireless protocols, error concealment, or data encoding within a radio frequency (RF) band to improve link quality. However, these solutions have been limited by RF congestion within an RF band, causing lower data rates and unreliable communication. The use of multiple RF bands (e.g., multi-band operation) may be complicated by the various frequencies available in different countries. Additionally, the amount of absorption of radio signals in typical user environments changes significantly with frequency of the signals. Furthermore, communications at different frequencies can require substantially different electronics in various cases.
What is needed in the art is an improved method of wireless communications between hearing assistance devices.